π–π and p–π conjugation, which is more efficient for intermolecular charge transfer in starburst triarylamine donors of platinum acetylide sensitizers?

•Two novel platinum acetylide sensitizers were synthesized and applied in DSSCs.•The introduction of π–π span group increased the donating and coplanar properties.•New absorption peaks around 410 nm of dyes were found due to the conjugative effect.•The span group in electron donors plays an important role for the design of sensitizers.

Two novel starburst donors based platinum acetylide sensitizers with π–π conjugated span group (2-vinylthiophene) were synthesized and applied in dye-sensitized solar cells (DSSCs). The photovoltaic performances of sensitizers were investigated by photophysical, photovoltaic, electrochemical, and a theoretical approach. Compared with similar triphenylamine based platinum acetylide sensitizers which do not contain a 2-vinylthiophene group, it was found that the introduction of 2-vinylthiophene as a span group increased the donating ability of donor and the coplanar property between the donor and π-bridge, which are in favour of the intramolecular charge transfer. Moreover, the new DSSCs based sensitizers displayed a power conversion efficiency of 2.80% and 2.95%, which is significantly improved over that determined for the non-vinylthiophene containing analogues.

Graphical abstractTwo novel starburst donor based platinum acetylide sensitizers with π–π conjugated span group (2-vinylthiophene) were synthesized and applied in dye-sensitized solar cells (DSSCs). This work demonstrated that the π–π span group in the electron donors plays a more important role in the sensitizers for the intermolecular charge transfer compared with p–π conjugation unit.Figure optionsDownload full-size imageDownload as PowerPoint slide